In electrical systems using plurality of batteries in parallel to extend operating life, premature battery failure can occur if one of the cells fails. When a battery fails or becomes extremely weak it frequently appears as a low resistance to the remaining batteries. Thus, the failure of one battery in a group of batteries can prematurely drain all of the batteries or cells.
The reliability of the multicell battery packages can be greatly enhanced by providing an isolation device between the cells to isolate the individual cells so that the premature failure of one cell does not affect the remaining cells. Groups of diodes have been used as isolation devices for this purpose. In systems utilizing two volts or less, diode isolation is not practical because silicon diodes have too large a voltage drop, thus, severely reducing the voltage available for the equipment attached to the battery. Germanium diodes have a lower voltage drop, which could make them marginally useful except for the fact that the high reverse leakage of these devices renders them relatively useless for isolation purposes.